Des Moines, Iowa (CNN) - The three GOP presidential candidates at the top of Iowa polls are taking aim at one another, with the surging man in third - Rick Santorum - trying to claw his way into the top two ahead of Tuesday's Iowa caucuses.

Santorum, buoyed by polling that shows he's gone from the near the bottom of the field to third behind Mitt Romney and Ron Paul, took aim at Romney a day before the contest that will kick off the GOP's 2012 presidential caucus and primary season.